The proposed studies examine the neuropsychological processes underlying the deficits in priming exhibited by patients with Alzheimer's disease (AD). Although AD patient's priming deficits have often been attributed to a breakdown in the organization of semantic memory, recent evidence suggests that other factors, such as inefficient semantic encoding, and deficient attentional or arousal processes may play significant roles. A determination of the particular processes underlying the AD patient's priming deficits may lead to important information about the necessary and sufficient conditions for the occurrence of the priming phenomenon, about the neural substrates mediating priming, and about the nature of the neuropsychological deficits associated with AD. The first set of experiments examines the status of arousal and selective attentional processes in AD patients using a series of simple, choice, and covert orienting of attention reaction time tasks. The second set of experiments examines the dynamics of activation within AD patient's semantic network using tests of direct, indirect and summation semantic priming as well as tests of retrieval from semantic memory. A third set of experiments examines the effects of manipulating arousal and attention on the priming performance of AD patients. A fourth set of experiments examines the relative contributions of perceptually-based and conceptually based semantic information to AD patient's priming performance. These studies are intended to shed light on the neuropsychological deficits associated with AD and enhance a deeper understanding of priming phenomena and their relevance to clinical applications.